“Theories are like toothbrushes,” it’s sometimes said. “Everybody has their own and nobody wants to use anybody else’s.”

It’s a joke, but when it comes to the study of consciousness – the question of how we have a subjective experience of anything at all – it’s not too far from the truth.

In 2022, British neuroscientist Anil Seth and I published a review listing 22 theories based in the biology of the brain. In 2024, operating with a less restrictive scope, US public intellectual Robert Kuhn counted more than 200.